Slag prevention air slots in furnace sidewalls

ABSTRACT

An apparatus for reducing slag deposits in the furnace section of a vapor generator in which a plurality of openings are formed in at least one of the walls adjacent a wall through which the furnace burners discharge. Air is continuously passed through the openings and across the heat absorption surface of the latter wall to maintain an oxidizing atmosphere and reduce the build-up of slag deposits on the wall.

United States Patent 1 Brown [111 3,867,909 1 Feb. 2 5,1975

[ SLAG PREVENTION AIR SLOTS IN FURNACE SIDEWALLS [75] Inventor: John A. Brown, Gulfport, Miss.

[73] Assignee: Foster Wheeler Corporation,

' Livingston, NJ.

22 Filed: Nov, 19,1973

21 Appl. No.: 417,319

[52] US. Cl 122/235 B, 110/75 R [51} Int. Cl. F22b 15/00 [58] Field of Search 122/235 R, 235 B; 110/75 R, 28 R, 28 S, 28 Q [56] References Cited UNITED STATES PATENTS 2/1927 Schwartz 110/28 S 8/1942 Rohrer 11/1954 Armacost 110/28 R 3,048,131 8/1962 Hardgrove 110/28 R 3,269,366 10/1974 Caracristi et a1. 122/392 3,662,719 5/1972 Winkin 122/235 R Primary Examiner-Kenneth W. Sprague Assistant Examiner-Larry l. Schwartz Attorney, Agent, or Firm-Marvin A. Naigur; John E. Wilson; Warren B. Kice [57] ABSTRACT An apparatus for reducing slag deposits in the furnace section of a vapor generator in which a plurality of openings are formed in at least one of the walls adja cent a wall through which the furnace burners discharge. Air is continuously passed through the openings and across the heat absorption surface of the latter wall to maintain an oxidizing atmosphere and reduce the build-up of slag deposits on-the wall.

7 Claims, 4 Drawing Figures 1 SLAG PREVENTION AIR SLOTS IN FURNACE SIDEWALLS BACKGROUND OF THE INVENTION This invention relates to a furnace structure and, more particularly, to a furnace structure having walls formed by a plurality of finned tubes for passing water in a heat exchange relation with the heat generated in the furnace. In these arrangements, a plurality of burners are usually associated with one or more walls of the furnace, with fuel being introduced through the burners and being combusted in the furnace to raise the temperature in the furnace to predetermined values.

In the use of fossil fuels in these type of environments, severe slag deposits are formed on the heat absorption surfaces in the furnace section during the combustion process. This, of course, severely curtails the efficiency of the generator and, in addition, results in an imbalance of heat absorption throughout the furnace section.

The above problem of slag deposits is compounded in furnaces having a hopper section formed by angling two opposing walls of the furnace inwardly to define a throat portion. In these arrangements, slag logs, which are formed by small pieces of slag removed by soot blowers or by gradual build-up of drips, form in the corners between the sloping walls and the vertical sidewalls and can either slide down the sloping walls and bridge the throat or build up to unacceptable levels. The problem is even further complicated by the fact that the corners between the sloping walls and the sidewalls are areas most likely to be operating at a reducing atmosphere which effectively reduces the ash softening temperatures of the slag and allows it to remain in a plastic, sticky state which renders it more difficult to remove by soot blowing.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a furnace structure in which the build-up of slag along the heat absorption surface of the furnace generator is reduced.

It is a further, more specific, object of the present invention to provide a furnace structure in which air is continuously blown across a portion of the heat absorption surfaces in the furnace interior.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of a vapor generator incorporating features of the present invention;

FIGS. 2 and 3 are cross-sectional views taken along the lines 2-2 and 33, respectively, of FIG. 1; and

FIG. 4 is an enlarged cross-sectional viewtaken along the line 4--4 of FIG. 1.

7 DESCRIPTION OF THE PREFERRED EMBODIMENT 12b and 14b convey water to be heated from lower headers 22 and 24, respectively, to upper headers 26 and 28, respectively, in a conventional manner, with it being understood that similar headers are provided for the finned tube sections 16b and 18b.

A furnace section, shown in general by the reference numeral 30, is formed in the lower portion of the vapor generator 10 with the finned tube wall sections 12b, 14b, 16b and 18b defining heat albsorption surfaces in the interior of the furnace section.

The lower portion of the furnace section 30 has a hopper section 32 which is formed by inwardly sloped lower portions of the walls 12 and 14 and which terminates in a throat section 34 for gravity expulsion of ash particles formed during the combustion process.

A windbox 36 extends around the upper portion of the furnace section 30 and supports three opposing rows of burners 38 which operate in a conventional manner to burn coal introduced thereto by a conveying means not shownand which discharge through openings 40 formed in the walls 12 and 14, respectively. A duct 42 supplies air to the windbox 36 which air is circulated through the openings 40 to aid in the combustion process, in a conventional manner.

The combustion gases formed in the furnace section 30 pass upwardly through a vertical gas pass 44 to a horizontal gas pass 46. Although not shown in the drawings, it is understood that a conventional downward vertical gas pass registers with the horizontal gas pass 46 for passing the gases to a stack, or the like.

According to a main feature of the present invention, a plurality of slots 50 are provided through two portions of each of the walls 16 and 18. The slots are formed through consecutive finned portions of the finned tube sections 16b and 18b and extend vertically, with their lower end portions being substantially coplaner with a portion of the sloping wall portions 12 and 14.

As better shown in FIGS. 2 and 3, a pair of seal boxes 52 and Marc mounted on the sidewall 16 and a pair of seal boxes 56 and 58 are mounted on the sidewall 18. The seal boxes 52, 54, 56 and 58 are welded,or otherwise directly fastened, to the outer surfaces of the finned tube sections 16b and 186 so that the boxes cover the slots 50. A plurality of ducts 60 connect the windbox 36 to the seal boxes 52, 54, 56 and 58 in order to supply air from the windbox to the slots 50 whereby the air is discharged in two directions directly across the sloping portions of the walls 12 and 14 as shown by the arrows in FIG. 3 in connection with the wall 14.

As stated above, this enables an oxidizing atmosphere to be maintained in'the furnace section 30, and particularly along the sloping portions of the walls 12 and 14, to maintain an oxidizing atmosphere in this area. Ancillary benefits of the arrangement of the present invention are that the air blowing across the above wall portions will not only maintain an oxidizing atmosphere, but will also blow away slag falls from the walls.

It is understood that the spacing between the slots 50, as well as their number and size, can be varied from that shown in the drawings. Also, the design may be such that the windbox 36 extends over and encloses the slots 50, in which case the seal boxes 52, 54, 56 and 58, as well as the ducts 60, can be eliminated.

Of course, other variations of the specific construction and arrangement of the apparatus disclosed above can be made by those skilled in the art without depart ing from the invention as defined in the appended claims.

What is claimed is:

l. A furnace structure comprising at least four walls interconnected to form an enclosure, at least a portion of said walls defining an internal heat absorption surface, burner means associated with at least one of said walls for burning a fossil fuel within said enclosure and adjacent said heat absorption surface, said wall associated with said burner means having a vertical portion and a sloped portion, a plurality of openings extending through at least one of the walls connected to said wall associated with said burner means, and means for supplying air to said openings, said openings being located relative to said wall associated with said burner means so that said air passes substantially perpendicular to said vertical portion of said wall and across said sloped portion and across the junction between said vertical portion and said sloped portion to continuously maintain an oxidizing atmosphere at the heat absorption surface defined by said portions.

2. The structure of claim 1 wherein said openings are in the form of a plurality of spaced slots aligned with said sloped portion and extending to said junction.

3. The structure of claim 1 wherein said burner means are adapted to discharge through two opposed walls of said enclosure.

4. The structure of claim 3 wherein said openings are formed through the two walls connected to said two opposed walls so that air is blown across said sloped portions and said junctions in two directions.

5. The structure of claim 1 wherein said openings are formed through the two walls connected to said wall associated with said burner means so that air is blown across said sloped portion and said junction in two directions.

6. The structure of claim 1 wherein said burner means are mounted adjacent the vertical portion of said wall associated with said burner and discharge through openings formed in said vertical portion.

7. The structure of claim 1 wherein said means for supplying air comprises a windbox extending around a portion of said enclosure to supply air to said burner means, and duct means connecting said windbox to said openings. 

1. A furnace structure comprising at least four walls interconnected to form an enclosure, at least a portion of said walls defining an internal heat aBsorption surface, burner means associated with at least one of said walls for burning a fossil fuel within said enclosure and adjacent said heat absorption surface, said wall associated with said burner means having a vertical portion and a sloped portion, a plurality of openings extending through at least one of the walls connected to said wall associated with said burner means, and means for supplying air to said openings, said openings being located relative to said wall associated with said burner means so that said air passes substantially perpendicular to said vertical portion of said wall and across said sloped portion and across the junction between said vertical portion and said sloped portion to continuously maintain an oxidizing atmosphere at the heat absorption surface defined by said portions.
 2. The structure of claim 1 wherein said openings are in the form of a plurality of spaced slots aligned with said sloped portion and extending to said junction.
 3. The structure of claim 1 wherein said burner means are adapted to discharge through two opposed walls of said enclosure.
 4. The structure of claim 3 wherein said openings are formed through the two walls connected to said two opposed walls so that air is blown across said sloped portions and said junctions in two directions.
 5. The structure of claim 1 wherein said openings are formed through the two walls connected to said wall associated with said burner means so that air is blown across said sloped portion and said junction in two directions.
 6. The structure of claim 1 wherein said burner means are mounted adjacent the vertical portion of said wall associated with said burner and discharge through openings formed in said vertical portion.
 7. The structure of claim 1 wherein said means for supplying air comprises a windbox extending around a portion of said enclosure to supply air to said burner means, and duct means connecting said windbox to said openings. 